It is purely coincidental. The lunar cycle is slowing down. A billion year ago, it was much shorter, may be just 16-20 days, I can't dig a link right now. The Earth-Moon system is gradually transforming its angular momentum from close&fast to far&slow (it's a tide effect, and at the same time, tides and other planets dissipate some of this momentum, but there is also a transfer from the rotation of the earth).

And the Earth days themselves are slowing down, they had fewer hours a billion year ago.

The Moon is already tide-locked with one side watching the Earth. Eventually if the system could go on long enough (it won't, the sun will blast it all earlier), the Earth would also become tide-locked with the moon, with a day that last weeks and the Moon further from the Earth than it is now.

And anyway, it's only western women who have a 28 days cycle, found this looking for a ref. on wikipedia:
http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=1340049&dopt=A bstractPlus

Pierre